linux-kernel - Re: [PATCH 6/7] RAS: Get CS fabirc ID register bit fields

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Date:   Thu, 26 Oct 2023 09:55:01 -0400
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Muralidhara M K <muralimk@....com>, linux-edac@...r.kernel.org,
        x86@...nel.org
Cc:     yazen.ghannam@....com, linux-kernel@...r.kernel.org, bp@...en8.de,
        mchehab@...nel.org, Muralidhara M K <muralidhara.mk@....com>
Subject: Re: [PATCH 6/7] RAS: Get CS fabirc ID register bit fields

On 10/25/2023 3:33 AM, Muralidhara M K wrote:
> From: Muralidhara M K <muralidhara.mk@....com>
> 
> Read correct register bit fields for cs_fabric_id for
> address translation to work.
> 

What is the problem exactly?

> Signed-off-by: Muralidhara M K <muralidhara.mk@....com>
> ---
>   drivers/ras/amd/atl/reg_fields.h | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/ras/amd/atl/reg_fields.h b/drivers/ras/amd/atl/reg_fields.h
> index c3853a25217b..6b60091f235b 100644
> --- a/drivers/ras/amd/atl/reg_fields.h
> +++ b/drivers/ras/amd/atl/reg_fields.h
> @@ -28,14 +28,14 @@
>    *	Rev	Fieldname	Bits
>    *
>    *	D18F0x50 [Fabric Block Instance Information 3]
> - *	DF2	BlockFabricId	[19:8]
> + *	DF2	BlockFabricId	[13:8]

DF2 should be [15:8]

>    *	DF3	BlockFabricId	[19:8]

DF3 should be [13:8]

>    *	DF3p5	BlockFabricId	[19:8]
>    *	DF4	BlockFabricId	[19:8]
> - *	DF4p5	BlockFabricId	[15:8]
> + *	DF4p5	BlockFabricId	[19:8]

DF4p5 is correctly listed as [15:8].

Special cases can be listed separately.

>    */
> -#define DF2_CS_FABRIC_ID	GENMASK(19, 8)
> -#define DF4p5_CS_FABRIC_ID	GENMASK(15, 8)
> +#define DF2_CS_FABRIC_ID	GENMASK(13, 8)
> +#define DF4p5_CS_FABRIC_ID	GENMASK(19, 8)
>   

Even though the most significant bit changes between DF versions, it 
looks like the upper bits are all reserved/Read-as-Zero. So we can 
document the correct field, and use an expanded/inclusive field (like 
[19:8]) for code simplification. And make a note of this for reference.

Thanks,
Yazen